Process for cooling granular materials being mixed

ABSTRACT

An apparatus and process for cooling of fine to coarse grained mixing materials, for example, dryblend, PVC agglomerate or granulate, etc., whereby the individual particles of mixing material are moved along an essentially closed circular or similar path and at the same time are passed against cooled surfaces, in conjunction with mixing within a cooling mixer. Several embodiments of cooling mixers are described in which the wall and, if desired, the bottom is made with double walls through which a coolant flows and on or in which a rotatable means for moving periodically compacting and turning over of the mixing material have been provided. The mixing elements and compacting elements can be cooled by internal cooling flow. Various embodiments have rotatable compacting bodies swinging around or vertically reciprocated within the mixing container. Scraping elements prevent build-up of compacted materials on various surface areas.

United States Patent 11 1 Bremer Sept. 9, 1975 [54] PROCESS FOR COOLING GRANULAR 3,785,621 1/1974 Hoskins 259/102 MATERIALS BEING MIXED Primary Examiner-Albert W. Davis Jr. t B l G [75] Inventor remu- Merge weg ermany Assistant Examiner-Daniel J. OConnor [73] Assignee: Gunther Papenmeier KG Attorney, Agent, or FirmStrauch, Nolan, Neale, Nies Maschinenun Apparatebau, & Ku Detmold, Germany [22] Filed: Jan. 12, I973 [57] ABSTRACT 2 l] APPL N 323 079 An apparatus and process for cooling of fine to coarse grained mixing materials, for example, dryblend, PVC agglomerate or granulate, etc, whereby the individual Forelg Apphcat'o Pnonty Data particles of mixing material are moved along an essen- Jan. 19, 1972 G rm ny H 2202455 tially closed circular or similar path and at the same time are passed against cooled surfaces, in conjunc- 259/I02 tion with mixing within a cooling mixer. Several eml l (12 B44F D013 bodiments of cooling mixers are described in which Field of Search 2 165/92 the wall and, if desired, the bottom is made with double walls through which a coolant flows and on or in [56] References Cited which a rotatable means for moving periodically com- UNITED STATES PATENTS pacting and turning over of the mixing material have 2 115,742 5/1938 Newton ,1 259/102 been Provided- The mixing elements and Compacting 2,238364 4/[941 Prat [/92 elements can be cooled by internal cooling flowv Vari- 2,255,986 9/1941 Rapisarda., /30 ous embodiments have rotatable compacting bodies 2,573,709 11/1951 Hill 165/92 swinging around or vertically reciprocated within the 3.248,76l 5/l966 Mcllvaine H 2 mixing container. Scraping elements prevent build-up 31386-309 6/1968 Massoubrcw [65/92 of compacted materials on various surface areas. 3,407,046 lO/l968 Mass0ubre.... 165/92 3,410,533 11/1968 Penney .1 165/92 3 Claims, I2 Drawing Figures I ll PATENTEDSEP ems sum 1 of 4 PATENTED sEP 9197s SHEET 3 0F 1 PATENTEDSEP 9|975 SHEET 0F 4 PROCESS FOR COOLING GRANULAR MATERIALS BEING MIXED BACKGROUND OF THE INVENTION As taught in the German published application No. 1,270,536, a process for cooling of granulated, gellike or similar plastics, etc., in a mixer has been known. That mixer includes container walls and annular components through which coolants flow and between which the mixing material is moved by a mixing device through which, preferably, a coolant also flows. With that apparatus it was possible to decrease considerably the cooling time as compared to that in mixers without additional cooling components, but in such case there still remained a problem in that the surface layers of the particles of the mixing material, which at times are full of fissures, make insufficient contact, mostly only punctiform, with the available cooling surfaces. This factor coupled with the poor heat conductivity of the plastics or granular materials which are being mixed and are to be cooled, have an unfavorable effect on a quick heat transfer from mixing material to the cooling surfaces.

Furthermore, a cooling mixer has been proposed with cooling components rotating together with the mixing tool and rising helically counter to the rotating direction, whereby a more intensive contact of the par ticles of the mixing material and cooling surfaces is to be achieved by increase of the reciprocal relative speed. However, that apparatus, beside the disadvantage of the previously mentioned cooling mixer still has the disadvantage of an increased friction, again decreasing the cooling effect.

SUMMARY OF THE INVENTION The present invention is based on the objective of developing a process for cooling of fine or coarse grained mixing material, as well as of a cooling mixer to carry out the process, whereby the cooling performance despite the poor heat conductivity of plastics is to be increased by intensifying the heat transfer between the particles of the mixing material and the cooling sur faces as compared to known processes or apparatus.

This is achieved according to the invention, by a pro cess of the initially mentioned type, in the case of which however at least partial quantities of the mixing material are condensed or compacted additionally in periodically repeated operating methods and are again broken up during the succeeding relaxing from the compaction. Preferably, the pressure exerted thereby repeatedly for brief periods is high enough, so that the elastically deformable particles of the mixing material are easily pressed flat.

In this manner one will obtain substantially enlarged contact surfaces of the particles, which fit closely on the cooling surfaces. As a result, the heat transfer is extraordinarily intensified despite the poor heat conductivity of plastics, as compared to the unfavorable point contact of material particles in the case of known processes. At the same time, only a relatively small deformation energy is added to frictional energy of the mixing material which, compared to the increased heat transfer obtained because of the manifoldly enlarged contact surfaces, can be disregarded,

Advantageously the mixing material is compacted between rolling surfaces and is again broken up later on while the material is relaxing. Gradually, all particles of mixing material are cooled more quickly than hitherto in a periodically repeated sequence of compacting and breaking up, without there being any need to put up with too high a mechanical load, harmful to the quality of the mixing material. At the same time, the speed of the operating process can be controlled by careful adjustment of the compacting pressure, which must be exerted on the particles of the mixing material to mechan ical loading capacity of the mixing material that is to be cooled.

This process is carried out according to the invention with a cooling mixer of the initially mentioned type, which has at least one body with circular base rotatable around its axis and disposed in the inside space of the container, whereby the at least one of the rotating bodies has a surface area closed upon itself in a known manner, and is disposed parallel; but eccentrically to the middle axis of the container or while enclosing an angle with said axis in such a way, that a gap is formed between the rotating body and the container wall or the container bottom or a further rotating body, through which gap the mixing material is moved.

The surface of the rotating body, advantageously, is movable toward the container wall or the container bottom, whereby contact pressure means can be provided for the rotating body opposite the container wall. Effectively, an adjusting and regulating arrangement for the contact pressure means is provided. In this way an adaptation of the pressure exerted on the particles of the mixing material is made possible, which is an advantage especially in case of substances with a variable mechanical loading capacity.

In a further embodiment of the invention, means can be provided for the production of a rotary movement of the rotating body around the axis of the container, which means comprise advantageously a revolving drive shaft disposed in the area of the container axis and an arm attached thereto and carrying the rotating body. Such an arrangement guarantees a uniform cooling of the mixing material.

Furthermore, driving agents for the production of a forced rotary movement of the rotating body around its own axis can be provided, which comprise a toothing disposed on the rotating body and an inside toothing on the container wall or a gear rim on the drive shaft. In this manner the entry of the mixing material into the gap between the rotating body and container wall can be increased or decreased.

Especially for cleaning purposes, an effective arrangement for adjustment of the rotating body in an axial direction is provided. At the same time the arrangement for the conveyance of the rotating body can comprise a drive shaft reciprocable in an axial direction.

Effectively, stripping elements for cleaning the container wall and/or the rotating bodies of adhering particles of mixing material are also provided; this is of advantage particularly in the case of high temperatures of the mixing material and in the case of relatively high operating pressures. The stripping elements in this case can consist of scrapers movable relative to these surfaces and disposed in the immediate vicinity of the surface of the rotating body or of the inside wall of the container, which scrapers are mounted on carrying arms swivellable around the axis of the body or of the container.

The development of the surfaces is not restricted to cylindrical shapes. For reasons of adaptation to the form of the container, its position in the chamber and of the mixing material that is to be processed, it can be advantageous, to provide at least one rotating body with a cone-shaped surface. It is also possible to provide two cone-shaped rotating bodies or one coneshaped rotating body and one ring concentrically with the container axis in the container.

The rotating body can also consist of a ring, freely movable in relation to the container bottom and concentric to the container axis, which is pressed against the container bottom by its gravity or also possibly other means of pressure, and which is lifted upwards periodically by the conveyed mixing material or constructional means, such as cams, so that a hopping movement results for periodically compacting the mixing material and then permitting its relaxation in accord with the process of the invention.

Each of the rotating bodies can be made with cooling passages as by using double walls and can utilize a cool ing agent flowing through them, so that the operating time will be considerably shortened.

Since it is necessary to loosen the mixing material along the cooling surfaces between compacting, means for moving or turning over of the mixing material must be provided. These means can consist of a mixing tool, known per se, of drawing in elements arranged on the rotating body, or of a device for blowing in of air or gas by means of nozzles disposed in the area of the container bottom and/or the container wall. In addition a mechanism for sucking off of the heated air can also be provided for this purpose preferably in the upper area of the container wall or on the lid of the container, as a result of which the cooling process can be still further accelerated without any extensive expenditure in apparatus.

The object of the invention will be explained in detail on the basis of several preferred embodiments shown in the drawing by way of examples.

FIG. 1 shows a schematic presentation of a part of a cooling mixer with rotational body in section;

FIGS. 2 and 3 show views in schematic presentation with various rotating bodies from above;

FIG. 2a shows a contact pressure means for the rotating bodies and an alternative to the one in FIG. 2;

FIG. 4 shows the construction and arrangement of a conical rotating body;

FIG. 5 shows in schematic presentation the arrangement of two conical rotating bodies in a perpendicularly arranged cooling mixer;

FIG. 6, shows two rotational bodies, developed in a perpendicularly arranged cooling mixer;

FIG. 7, shows the combination of a rotatable, cylindrical cooling ring with a conical rotating body in the perpendicularly disposed cooling mixer;

FIG. 8, is a cylindrical rotating body, disposed in the cone-like lower part of a cooling mixer;

FIG. 9, shows the arrangement of a rotating body in the perpendicularly disposed cooling mixer hovering (suspended) on the mixing material;

FIG. 10, shows a cooling mixer, revolving around its horizontal axis, with a cylindrical rotating body rolling on the mixing material; and

FIG. 11, shows the arrangement of a cylindrical rotating body in a cooling mixer, the rotational axis of which is at a slant in relation to the horizontal.

The cooling mixer shown in FIG. 1 has a container 10 with a double side wall 11 through which a coolant flows, and with a double walled bottom 12 through which coolant also flows, and through which the drive shaft 13 for a mixing tool 14 is guided centrally. On drive shaft I3, which is driven by a motor (not shown) disposed below the container 10 and which shaft extends to a location near the upper edge of the container, there sits a bipartite carrier arm 15, which carries a rotating body 16. The two parts l7, 18 of the carrier arm 15 are connected with one another on a hinge joint, and their combined length at mutual alignment is sufficient so that even when the surface 19 of the rotating body 16 fits against the container wall 1 l, the arms cannot be aligned, they are angular, i.e., their disposition is at an angle. The two parts l7, 18 of the carrying arm are biased by a suitable pressure agent, such as a spring 20 (FIG. 2) or a hydraulic piston 21 (FIG. 2a) in the direction of their mutual alignment and thus the rotating body 16 (is pressed) against the inside wall 11 of the container. The rotating body preferably has coolant passages, e.g., a double wall, and coolant flows through it. Its surface 19 is adapted to the contour of the container wall 11 and of the container bottom 12 especially in their region of transition 22.

During rotation of the mixing tool 14 in the container 10, the rotating body 16 is moved simultaneously through the mixing material via the drive shaft 13 and carrying arm 15, and rolls off during this movement in relation to the container wall 11. At the same time the mixing material is drawn into the gap 23 formed between the rotating body 16 and the container wall 1 1, and is compacted between the surface 19 of the rotating body 16 and the container wall 11; subsequently whenever the rotating body 16 is again turned farther, the just compacted mixing material is again relaxed and at the same time broken up (loosened up) again by the mixing tool. This breaking up is desirable to enable an easy movement of the rotating body 16.

At the same time the elastically malleable particles of the mixing material at these surfaces are easily pressed flat and as a result the surface needed for the heat transfer is greatly multiplied. The contact pressure, while being determined by the construction of the device, the rotational speed, the quantity of the mixing material and other characteristics, is also determined by the level of the pressure exerted by the spring 20 or the piston 21. This pressure can be adapted, sensitively possibly by adjustment of the pressure agent, to the pertinent requirements.

FIG. 2 shows a top view of a horizontally arranged, schematically shown cooling mixer with two rotating bodies 16. Their basic structure and arrangement corresponds essentially to the one according to FIG. I. The mixing tool 14 is only schematically indicated and can have hooklike ends. The spring 20 differing from the embodiment according to FIG. 1 is attached directly on the drive shaft 13. The mixing material compacted in the gap 23 is indicated by dark coloring.

FIG. 3 is a top view schematically showing a further embodiment of a cooling mixer 10 which has only one rotating body 16, the diameter of which is about as large as half the diameter of the mixing container 10. While this was not necessary for the embodiment according to FIG. 2, in this case the carrier arm 15 must be disposed below the rotating body 16. Since furthermore only one rotating body is provided, a counterweight 25 is disposed on a second arm 24, mounted on the drive shaft 13, which counterweight rotates together with rotating body 16. Effectively a stripping element 26, which glides along the container wall 11, is disposed at the end of this am 24 or of the weight 25, and frees said wall of adhering particles of mixing material. The outer part 18 of the carrying arm likewise carries a stripping element 27, the surface area 19 of the rotating body 16 moving past it during rolling off and thus freeing it of adhering particles of mixing material.

In both embodiments, according to FIGS. 2 and 3, cooling of the rotating bodies 16 can be accomplished by a fed-in coolant. One can also use a hydraulic piston 21 according to FIG. instead of the spring 20 as a pressure means. It is possible to operate without a pressure means whenever the outward pressure exerted during rotation of the rotating bodies as a result of the centrifugal force suffices. In such case, adjustment of the pressure to the mechanical loading capacity of the mixing material can be accomplished simply by regulation of the r.p.m. It can possibly even be effective to provide a spring 20 acting in reverse direction, for example between the drive shaft 13 and the rotational axis of the rotating bodies 16, in order to counteract the centrifugal force. It is to be understood that stripping elements 26 and 27 can also be provided in the embodiment according to FIG. 2.

In order to increase or decrease the quantity of mixing material drawn into the gap 23, the rolling-off movement of the rotating bodies 16 on the container wall 11 can be replaced by a forced rotational movement of the rotating bodies, whereby the driving means can consist of customary toothings, etc. For purposes of cleaning and servicing, the drive shaft 13 can be removable in a known manner. Instead of or in addition to a mixing tool I4, an arrangement for blowing in and possibly also for sucking off of air in inert gas can be provided, as a result of which the loosening up of the mixing material and the cooling time can be influenced favorably.

FIG. 4 shows the arrangement and development of further embodiment of a rotating body, which can be used in the examples according to FIGS. 2 or 3.

As can be scen from FIG. 4, a rigid axle 28 for the reception of a bearing 29 with a rubber torsion spring 30 in a protecting cap 31 is located perpendicularly on the end of the carrying part 17. The second carrying part 18 is mounted on the bearing 29. An axle 32 is set rigidly perpendicularly to and in the part 18 of the carrying arm, which has on two sections means 33 for the axially rotatable mounting ofa conical rotating body 16a. A stripper 27 fits against the rotating body 160, which is attached to the part 18 of the carrying arm.

The rotating body 16a, according to FIG. 4 has a conical shape, whereby the upper and lower area can be in accordance with the broken lines, it has components 34 for the forcible guidance of the coolant and is supported by means of spokelike struts 35, through which coolant flows, on the distributor pipe 36 for the coolant and the distributor head piece 37 for the coolant with a packing pushing 38. The packing bushing 38 is at tached to a water-ring-packing box 39, through which the cooling water can enter or drain via hoselines etc.

In the case of this development or arrangement of the rotating body, a compacting area develops in the gap 23 for the mixing material that is to be cooled by centrifugal action from the pressure producing rotating body 160, whereby the rubber torsion spring 30 has an effect of reinforcing the centrifugal force.

Further advantageous embodiments of the invention are shown schematically in FIGS. 5 to 11 in cooling mixers arranged vertically, horizontally or slantingly.

At the same time 16b designates a conical rotating body, a double cone shaped rotating body, 41 a rotating body hovering or hopping on the mixing material, 40 a conical lower part of a mixing container, and 42 a mixing container, the rotational axis of which is slanted in relation to the horizontal. The illustrated forms of the mixing container per so are already known and used in practice and it has been determined that the rotating bodies in accord with the present invention can be utilized advantageously in such containers.

In the case of the cone-shaped rotating-bodies 16b and 16a (FIGS. 5 to 7), the compacting gap 23 is wedge shaped and particularly narrow, which can be of conside'rable importance in view of avoiding obstructions of mixing material in the catchment drainage area of the rotating bodies. In the case of an arrangement according to FIG. 7 a further compacting area occurs between the two rotational bodies. In that case, the diameter of the cylindrical rotational body 16 will, for practical purposes, be smaller than the largest diameter of the cone shaped rotational body 16b. The diameter of the rotating body 16 of the type shown in FIGS. 8, 10 and 11, is considerably smaller than that of the con tainer, which in turn results in a relatively narrow compacting gap 23. Suitable means will effectively limit the downward movement of the hopping rotating body in order to prevent a shoring up of the rotating body 41 on the mixing tool.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. Process for cooling of mixing material in which the individual particles of the mixing material are elastically deformable, including the steps of moving the individual particles of the mixing material on effectively closed paths and at the same time gliding the particles past cooled surfaces and periodically subjecting at least parts of the quantities of the moved mixing material to an additional cooling by means of cooled surfaces, the particles of said parts of the quantities of the moved mixing material being compacted under light flattening for a short time during the additional cooling process, whereby the heat contact areas of said particles are enlarged, said particles being loosened up by a loosening member during a relaxation period which follows the compaction period.

2. Process as defined in claim I, characterized in that the compacting pressure exerted briefly and repeatedly on the particles of the mixing material is sufficiently high that the elastically deformable particles of the mixing material are easily pressed flat.

3. Process as defined in claim 1, characterized in that the mixing material is compacted between surfaces rolling off on one another. 

1. Process for cooling of mixing material in which the individual particles of the mixing material are elastically deformable, including the steps of moving the individual particles of the mixing material on effectively closed paths and at the same time gliding the particles past cooled surfaces and periodically subjecting at least parts of the quantities of the moved mixing material to an additional cooling by means of cooled surfaces, the particles of said parts of the quantities of the moved mixing material being compacted under light flattening for a short time during the additional cooling process, whereby the heat contact areas of said particles are enlarged, said particles being loosened up by a loosening member during a relaxation period which follows the compaction period.
 2. Process as defined in claim 1, characterized in that the compacting pressure exerted briefly and repeatedly on the particles of the mixing material is sufficiently high that the elastically deformable particles of the mixing material are easily pressed flat.
 3. Process as defined in claim 1, characterized in that the mixing material is compacted between surfaces rolling off on one another. 